Electronic combination locks have been known for many years. Recently, self-powered electronic combination locks have become well-known throughout the security industry in the form of the X-07 Electronic Combination Lock, the Cencon Lock and the Auditcon Lock, all sold by Mas-Hamilton Group of Lexington, Ky. All of these locks are self-powered electronic combination locks having a generator contained within the lock and manually operated by the operator at the time of lock opening in order to provide power to the electronic controls of the lock. The use of the manually powered mechanical drive to rotate a portion of the stepper motor which functions as a generator to produce the necessary power for the electrical operation of the lock eliminates the need for electrical power supply wiring from outside the lock or the use of a battery and the concomitant problems associated with batteries, such as aging, discharge and/or corrosion.
The stepper motor/generator of the electronic combination locks are capable of producing open circuit voltages well in excess of approximately sixteen volts during manual rotation, sufficient to charge capacitors to a level adequate to power the lock.
Due to size and space constraints within an electronic lock, the capacitor typically used with the X-07, Cencon and Auditcon Locks lacks the storage capacity to power the electronic control and provide the electrical current and power to operate a solenoid which may be used to control the mechanical chain of parts to drive the bolt from the extended position to a retracted, unlocked position.
Without an external or battery power source, a typical solenoid consumes too much power to pick and hold for the device to be practical in very low-level powered devices. The relatively large power consumption of a solenoid has dictated that electronic locks use either an alternative low-power consumption device such as a pulsed stepper motor, which has stable states as in the above Mas-Hamilton locks, or a battery or utility power supply connection in order to provide adequate power for a solenoid controlled device. The power source must maintain sufficient electrical power to operate the electrical controls of the lock pick and hold the solenoid or other device such as the stepper motor until the lock is unlocked and the bolt control activated to permit the retraction of the bolt.
Examples of solenoid controlled locks include U.S. Pat. No. 5,307,656 issued to Gartner, et.al. and U.S. Pat. No. 4,831,851 issued to Wayne F. Larson. The Gartner, et.al. lock is not disclosed as self-powered and, accordingly, a power supply such as a utility power source or a battery typically would be required to ensure operation of the lock, and the Larson lock is battery powered.
Solenoids have a characteristic of magnetically sealing the armature in an actuated position as a result of the coercitivity of the solenoid core and the residual magnetism in the body of the solenoid. This magnetic sealing and holding is normally addressed as an undesirable characteristic by the inclusion of a non-magnetic spacer between the solenoid body and the armature plate of the solenoid. The non-magnetic spacer prevents the armature plate from being pulled close enough to the solenoid body to be retained by the residual magnetic field of the core and solenoid.
If the spacer is removed and the sealing of the armature to the solenoid body permitted, the pulse solenoid will pick and hold until the magnetic seal is released by physical force exerted on the solenoid armature.
This magnetic sealing may be advantageously used in the right circumstances to permit the use of a much shorter and smaller pulse of energy by the solenoid in order to derive the desired mechanical displacement and mechanical action necessary to the operation of the lock.